This invention relates to an apparatus and method of forming gaskets, and, in particular, to a method and device for forming a patterned gasket as, for example, between an ink supply unit and a printhead of an ink jet printer.
As is well known, thermal ink jet printers use print cartridges in which thermal energy that is selectively produced by resistors located in capillary-filled ink channels near channel terminating nozzles or orifices, vaporize the ink momentarily and so form bubbles on demand within selected channels. Each temporary bubble so formed causes an ink droplet to be expelled and propelled toward a proximately supported recording medium. The print cartridge may be incorporated either movably in a carriage type printer or fixedly in a pagewidth type printer. The carriage type printer generally has a relatively small print cartridge, containing the ink channels and nozzles. The print cartridge usually consists of a printhead that is sealingly attached to a disposable ink supply unit. In use, the print cartridge mounted on a movable cartridge is reciprocated to print one swath of information at a time on a stationarily held recording medium, such as paper. After a swath of information is printed, the paper is stepped a distance equal to the height of a printed swatch, so that the next swath printed will be contiguous therewith. The procedure is repeated until an entire page is printed. For an example of a carriage type printer, refer to U.S. Pat. No. 4,571,599 to Rezanka.
In contrast, a pagewidth type printer has a stationary print cartridge having a length equal to or greater than the width of the recording medium or sheet of paper. The paper, in this case, is continually moved past the fixed or stationary pagewidth print cartridge and in a direction that is normal to the axis of the print cartridge. For an example of a pagewidth type printer, refer to U.S. Pat. No. 4,463,359 to Ayata et al., especially FIGS. 17 and 20 entitled "Fabricating Process for Large Array Semiconductive Devices," filed Dec. 5, 1988, and assigned to the same assignee as the present invention.
U.S. Pat. No. Re. 32,572 to Hawkins et al. discloses a thermal ink jet printhead and method of fabrication. As disclosed, a plurality of printheads may be concurrently fabricated by forming a plurality of sets of heating elements with their individual addressing electrodes on a first substrate, generally a silicon wafer, and by etching corresponding sets of channel grooves with a common recess for each set of grooves in a second substrate or silicon wafer. The first substrate and second substrate are then aligned and bonded together so that each channel groove has a heating element aligned therewith. Individual printheads are then obtained by milling away unwanted substrate or silicon material in order to expose the addressing electrode terminals, and by dicing the substrate into separate printheads. To form a print cartridge, each printhead is later sealed to an ink supply unit (to be discussed below).
U.S. Patent No. 4,567,493 to Ikeda et al. and U.S. Pat. No. 4,577,202 to Hara disclose a liquid jet recording head, including a plurality of protection layers, one of which has a region that directly contacts the liquid. A principal function of the protection layer is to prevent penetration by the liquid and therefore prevent a failure mode for the bubble generating resistors and their addressing electrodes. Hara discloses in FIG. 2b a tubing connection 220 and the patent to Ikeda et al. omits details of the ink supply unit interface.
U.S. Pat. No. 4,935,750 issued to Hawkins and commonly assigned with this application suggests the general concept of depositing by a photo-patterning or a screen-printing process, a compliant gasket material, such as silicone, around thermal ink jet printhead ink inlets. The surface of the deposited material is then coated with a reflowable and curable adhesive for subsequent use as a `dry` gasket for attaching and sealing the printhead to an ink supply unit to form a thermal ink jet print cartridge.
The suggested photo-patterning process involves intensive photolithographic printing and etching of the sealing material, and is, therefore, relatively more expensive than competitive processes. Gaskets formed by this process are of the dry type because they are cured prior to excess sealing-surface material being trimmed. In their subsequent use to manufacture thermal ink jet print cartridges, which require precise and effective sealing around each, or around a few of the, minute ink inlets of an array of such inlets, dry gasket seals have not proven to be as precise and effective as desired.
On the other hand, the screen-printing process involves the use of a screen and a squeegee device for forcing sealing material through the screen. As such, screen-printing has also not proven to be as economical, or as precise and effective as desired for print cartridge manufacture. The gasket seals produced by the screen-printing process are of the `dry` type as described under U.S. Pat. No. 4,935,750. Accordingly, the gasket seals produced by this method also are not as precise and effective in sealing around each or around a few minute ink inlets of an array of such inlets in a thermal ink jet print cartridge. In addition, each screen used in the screen printing process has a fixed thickness and gasket pattern therein and, therefore, cannot be varied to produce thinner or thicker gasket beads. Furthermore, because the screens are exposed during use, the gasket material tends to cure and dry on portions of each screen during such use, thereby requiring frequent and costly cleaning, or thereby distorting the shape, size and hence the effectiveness of subsequently produced gasket beads.